Sia found her adopted son on television

Sia says motherhood is the "best thing she's ever done". Photo / Instagram

Australian singer-songwriter Sia is "obsessed" with reality TV shows and decided to adopt her son after she spotted him on the programme she watched and tracked him down.

Speaking about how she came to adopt her sons, the "Chandelier" star said: "I am obsessed with reality television and documentaries, and I watched a documentary and saw my son. I was like, 'What? Like, he doesn't have anybody. Oh my god. I'm going to find him and I'm going to be his mummy.' And so that's what I did."

The 44 year-old singer insists motherhood is the "best thing she's ever done".

She added to Australia's Vogue magazine: "Motherhood is the best thing I've ever done. It's one of the hardest, but I have obviously such an overflow of love that I could definitely see myself doing it again, but not for a while.

The next thing I'm planning to do is foster actual infants.

"Maybe [their mother] is drug-addicted and then I could help look after them until, you know, their mum can get back on the wagon or an adoptive home is found. If I can do that then I think I'll feel like I'm superhuman."

Sia previously revealed she is "learning how to be a mother".

Asked about her new responsibilities as a grandmother on 'The Kyle and Jackie O Show' in Australia, she said: "I've decided to stop talking about it.

I made a bit of a boo-boo because they're my new children.

"I've only had them for a year. I'm such an open book that I forget not everyone else is.

While I didn't get into trouble for blabbing about his [her son's] children - I was peeing, which is where I have my best thoughts, and I realised that it was not my news to share with the world ... I instantly realised I can't talk about my children's private lives. I'm just learning how to be a mother."